Bought many LM3914 (VU-meter style 10 LEDs driver), now what to build?!?

[RoGeorge]

Got a bag of LM3914, NOS from the '90s, made by National Semiconductor. 

LM3914 - Dot/Bar Display Driver

The LM3914 is a monolithic integrated circuit that senses
analog voltage levels and drives 10 LEDs, providing a linear
analog display. A single pin changes the display from a mov-
ing dot to a bar graph. Current drive to the LEDs is regulated
and programmable, eliminating the need for resistors. This
feature is one that allows operation of the whole system from
less than 3V.

• Drives LEDs, LCDs or vacuum fluorescents
• Bar or dot display mode externally selectable by user
• Expandable to displays of 100 steps
• Internal voltage reference from 1.2V to 12V
• Operates with single supply of less than 3V
• Inputs operate down to ground
• Output current programmable from 2 mA to 30 mA
• No multiplex switching or interaction between outputs
• Input withstands ± 35V without damage or false outputs
• LED driver outputs are current regulated, open-collectors
• Outputs can interface with TTL or CMOS logic
• The internal 10-step divider is floating and can be referenced to a wide range of voltages

(from LM3914 datasheet, https://www.alldatasheet.com/datasheet-pdf/pdf/8898/NSC/LM3914.html )



It was an impulse buy, don't ask why.  I have no regrets.  ^-^
Looking for interesting applications, any ideas are welcome.

[ledtester]

There's always this idea...The PDF contains the fill-page ad for the device.

[RoGeorge]

I'm thinking as a first test to make a Li-ion single-cell discharges (to measure the mAh of phone batteries):
    - the idea is to use the constant current in the LM3914 LEDs to make a 20-200mA adjustable constant current load
    - the LEDs will draw their current from the DUT Li-ion battery
    - the mAh can be deduced by counting the total time during which the DUT battery was able to keep the LEDs on

    - a trim-pot could set the number of LEDs always on (so to set the discharging current according to the battery capacity)
    - LM3914 can be powered with as low as 3V, so it might work to self-power the entire circuit from the DUT it discharges 
    - the on-chip Vref should be good enough to keep the current constant while discharging from 4.2V to 3V
    - should use red LEDs, for their lower V_f drop, to let some margin for the IC open collector BJTs while the DUT approaches 3V

[themadhippy]

I used one years ago to make a power up/down sequencer,simple ramp generator to the input and relays on the outputs.

[Doctorandus_P]

LM3914 is the linear version. For the "VU" meter, you would want the LM3915, which has a logarithmic scale for the resistor string

Oopsie, I forgot about the LM1916, so read on to the next comment.

[themadhippy]

For the "VU" meter, you would want the LM3915,

the lm3915 is equal 3db steps ,for proper vu metreage its the lm3916 you wants

[oPossum]

.

[UnijunctionTransistor]

If you don't find enough projects to consume all of the ICs, you can always sell them.
NOS National Semiconductor LM3914s command attractive prices.

But are you sure that they are legit?

[RoGeorge]

That should be fun, thanks. 
The date/name stamp suggests you just drawn that, or is it a copy/paste?  I'm interested what editor was used to draw the schematic.

[RoGeorge]

But are you sure that they are legit?

Bought them from a brick and mortar shop, the seller is also the shop owner.  I think those are genuine NOS parts.  Bought them to build funny things, not for reselling.  I don't even have an eBay account.

[oPossum]

That should be fun, thanks. 
The date/name stamp suggests you just drawn that, or is it a copy/paste?  I'm interested what editor was used to draw the schematic.

Yes, it is my design. Drawn in Eagle 7.

I got some LM3914 clones that I had to test. There are at least three brands of LM3914/15/16 clones. Two are available from LCSC.

https://www.lcsc.com/product-detail/C53199171.html
https://www.lcsc.com/product-detail/C55109573.html

Here is a video showing that circuit and a 555 + 393 quadrature circuit.

[RoGeorge]

Clever those 4 LEDs! 

[oPossum]

Clever those 4 LEDs! 

Original design by Rue Mohr

https://bsky.app/profile/ruenahcmohr.bsky.social/post/3mvdggliwuk2l
https://bsky.app/profile/ruenahcmohr.bsky.social/post/3mvcka7szp222
https://bsky.app/profile/ruenahcmohr.bsky.social/post/3mvcikmr3zc22

I don't like using op-amps as comparators, so I 'fixed' it.